1. Field of the Invention
The present invention relates to an optical elevation apparatus which elevates an optical system body within a predetermined angular range about a fixed point on the optical axis of an objective lens as a rotation center.
2. Description of the Related Art
For example, a fundus camera serving as an ophthalmic device employs an optical elevation apparatus which vertically elevates the optical axis of an objective lens about a fixed point in the vicinity of the pupil of an eye under examination as a rotation center in order to observe or take an image of the fundus of the eye under examination and its periphery. In such a conventional optical elevation apparatus, generally, an arcuate guide member having the fixed point as the center elevatably holds the fundus camera body.
The arcuate guide member is provided with, for example, an arcuate rack gear. A pinion gear meshing with the rack gear is rotated through a manipulation handle to elevate the fundus camera body.
Japanese Patent Laid-Open No. 7-000363 discloses a buffer means for canceling the gravitational force of a fundus camera body so as to reduce the manipulation force required for elevation.
In Japanese Patent Laid-Open No. 7-000363, as shown in FIG. 6, a buffer 3 is used as a means for balancing the gravity. The buffer 3 cancels the gravitational force of a fundus camera body 1, having a weight of about 10 kg, along an arcuate guide member 2. The buffer 3, however, has a drawback in that it largely projects from the side surface of the fundus camera body 1.